We have developed and applied mass spectrometry to enables us to rank the stabilizing effects of small molecules when bound to proteins, particularly those that are drug targets. The rational behind the approach is that when proteins bind to their cognate ligands they are stabilized and thereby offer resistance to gas phase unfolding. The extent of this resistance is then used to rank ligands for the stability they induce in the protein. During the course of this project we evaluated this procedure with a series of membrane and soluble proteins, with a range of different KD values and solubility requirements. Specifically we demonstrated stability induced by ligand binding to the soluble proteins transthyretin and streptavidin and to a series of membrane proteins including the human metalloprotease (ZMPSTE24).
Overall therefore the method and associated software that we have developed provides a novel means of studying the effects of ligand binding on proteins. It is of particular utility when the system under study can bind multiple ligands, such as in the case of oligomeric proteins, where the binding events are challenging to discern using other methods. We have shown that the method can interrogate the effects on stability from ligand binding to soluble proteins and, of particular note, we demonstrated that our method can be used to characterize the effects of lipid binding on membrane proteins. To our knowledge, there are no other experiments that can provide this information in such a direct manner. The detail required to implement this method has been described and software to conduct the analysis has been made widely available (
http://pulsar.chem.ox.ac.uk(öffnet in neuem Fenster)). To date close to 100 downloads have taken place from academia and we have received considerable interest from industry. Ultimately, our software will be licensed to pharma and will be used in our partnership research agreements through our spin out company OMass Technologies Ltd.
